1. Field of the Invention
This invention relates to a contraction-extension mechanism type actuator. More particularly, it relates to a contraction-extension mechanism type actuator provided with a small simply constructed drive mechanism and adapted to serve as a work module for a micromachine.
2. Description of the Prior Art
For the work of micromodules, the mechanism which discerns the environmental condition of an object under treatment and feeds it back to a control system is indispensable. A micromachine which is intended to perform work within a minute pipe measuring not more than 10 mm in diameter, for example, is required to move a visual sensor or a tactile sensor or a work module which is disposed on a module at the leading end such as of a tubular manipulator. Though no large forces are needed in driving the leading end of such a work module, the mechanism used for this driving is preferably small and simple and so constructed as to admit fine adjustment since the leading end of the work module additionally accommodates a mechanism for the work. This mechanism preferably imparts virtually no motion to the module itself and enables only the sensors disposed at the leading end of the module to be freely moved with a stroke approximately in the range of from 1 to 500 .mu.m, for example.
Among the conventional actuators furnished with a small and simple mechanism and so constructed as to admit fine adjustment is the piezzo-actuator which is used in a scanning type tunnel microscope (STM) as illustrated in FIG. 11.
This piezzo-actuator is provided with piezzo elements 151, 152 and 153 in the X, Y, and Z directions respectively so as to move a probe 154 in a selected direction by applying a voltage to the piezzo element assigned to the selected direction. At this time, the size of a motion of a sample 156 on a sample base 155 is controlled by suitably varying the voltage being so applied. The piezzo elements 151, 152, and 153 which are used herein are adapted to produce an adjustable voluminal change by the application of a voltage. This adjustable change is substantially proportional to the magnitude of the voltage applied. The piezzo-actuator as a whole can be fabricated in a size fit for accommodation within a micromachine.
Since the size of a stroke which can be generated by a piezzo-actuator of this type is about 1 .mu.m at most, it is incapable of freely moving such sensors as are disposed at the leading end of the module of the micromachine and cannot be adapted for this purpose.
An object of this invention, therefore, is to provide a contraction-extension type actuator which operates with a small and simple mechanism, offers no hindrance to other work units, adopts a construction capable of fine adjustment, imparts virtually no motion to the module itself, and enables only the leading end of the module to be freely moved with a stroke approximately in the range of from 1 to 500 .mu.m, for example.